Research On Time-Space Evolution Law And Early-Warning Of The Ground Surface Settlement In Metro Shield Tunneling

Nowadays, China has become one of the largest shield tunnel markets in metro construction in the world. In recent years, it is obviously that the urban environmental geotechnical accidents happened more and more which caused by unallowed stratum deformation and ground surface settlements during the shield tunneling. During the metro shield tunnel constructions under complex conditions, how to explain the time-space evolution mechanism and laws of the ground surface settlements, and then predict their time-space evolution process and achieve early warning system for them? It has become an important issue waiting for solving in modern shield tunnel construction.Profited from the related domestic and foreign research results and based on time series analysis and stochastic medium theory, this thesis proposes to use back analysis of geotechnical engineering, artificial intelligence, system identification methods to explain the time-space evolution mechanism and laws of the ground surface settlements, and achieve prediction and visualizational early warning for them in Wuhan Metro Lineâ…¡Yangzi river-crossing shield tunnel construction.Firstly, the relationship between construction safety risks and ground surface settlements in river-crossing metro shield tunnel is analyzed. This thesis point out that the focus and key to control construction safety risks and the accidents is prediction and controlling of the ground surface settlements in the land and river section during river-crossing metro shield tunnel construction.Ground surface settlement time series have key characteristics such as unequally space, small sample size, trend and autocorrelation. Ground surface settlement time series model based on Weibull-ARIMA and its complete modeling process and algorithms are proposed. And this model can explain the ground surface settlement time series in shield tunnel construction more efficiently and accurately than the Weibull model, or ARIMA models. The applications of this model can gain the time characteristic parameters in the ground surface settlement time series fast and accurately and fulfill their description and characterization.The three-dimensional displacement field is the scope and size of the spatial distribution of the ground surface settlement. In this thesis, the spatial distribution calculation of the ground surface settlements is presented using the improved stochastic medium theory. Additionally, multi-adaptive mutation particle swarm optimization (MAMPSO) algorithm is proposed for back analysis of the spatial distribution characteristic parameters in the ground surface settlements. MAMPSO algorithm has a high identification performance and accuracy with the traditional Powell algorithm and the basic PSO algorithm and provides a new method to analyze the spatial distribution law of the ground surface settlements.Shield tunnel construction process is a complex evolving system with time and space. The principle of modeling the time and space evolution system of the ground surface settlements during shield tunnel construction is illustrated in this thesis. Based on the MAMPSO, this paper proposes the Radial Basis Function Neutral Networks to establish the intelligent prediction model of the ground surface settlements. The modeling is equal to the nonlinear function optimization problem of the structure and parameters in RBFNN, which can be solved by MAMPSO.One of the most important applications of information technology in underground construction is the early warning system of the ground surface settlements during shield tunnel construction. Based on multi-source information fusion theory, the early warning model of the ground surface settlements engineering is proposed. The thesis use the model and other information technology to achieve the functions such as feature fusion and decision fusion for local and integrated early warning, provides early warning system which including waring identification, analysis, prediction, accessment and decision for the ground surface settlement during shield tunnel construction.